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Tobin RJ, Harrison LE, Tully MK, Lubis IND, Noviyanti R, Anstey NM, Rajahram GS, Grigg MJ, Flegg JA, Price DJ, Shearer FM. Updating estimates of Plasmodium knowlesi malaria risk in response to changing land use patterns across Southeast Asia. PLoS Negl Trop Dis 2024; 18:e0011570. [PMID: 38252650 PMCID: PMC10833542 DOI: 10.1371/journal.pntd.0011570] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2023] [Revised: 02/01/2024] [Accepted: 01/16/2024] [Indexed: 01/24/2024] Open
Abstract
BACKGROUND Plasmodium knowlesi is a zoonotic parasite that causes malaria in humans. The pathogen has a natural host reservoir in certain macaque species and is transmitted to humans via mosquitoes of the Anopheles Leucosphyrus Group. The risk of human P. knowlesi infection varies across Southeast Asia and is dependent upon environmental factors. Understanding this geographic variation in risk is important both for enabling appropriate diagnosis and treatment of the disease and for improving the planning and evaluation of malaria elimination. However, the data available on P. knowlesi occurrence are biased towards regions with greater surveillance and sampling effort. Predicting the spatial variation in risk of P. knowlesi malaria requires methods that can both incorporate environmental risk factors and account for spatial bias in detection. METHODS & RESULTS We extend and apply an environmental niche modelling framework as implemented by a previous mapping study of P. knowlesi transmission risk which included data up to 2015. We reviewed the literature from October 2015 through to March 2020 and identified 264 new records of P. knowlesi, with a total of 524 occurrences included in the current study following consolidation with the 2015 study. The modelling framework used in the 2015 study was extended, with changes including the addition of new covariates to capture the effect of deforestation and urbanisation on P. knowlesi transmission. DISCUSSION Our map of P. knowlesi relative transmission suitability estimates that the risk posed by the pathogen is highest in Malaysia and Indonesia, with localised areas of high risk also predicted in the Greater Mekong Subregion, The Philippines and Northeast India. These results highlight areas of priority for P. knowlesi surveillance and prospective sampling to address the challenge the disease poses to malaria elimination planning.
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Affiliation(s)
- Ruarai J. Tobin
- Infectious Disease Dynamics Unit, Melbourne School of Population and Global Health, The University of Melbourne, Melbourne, Australia
| | - Lucinda E. Harrison
- School of Mathematics and Statistics, The University of Melbourne, Melbourne, Australia
| | - Meg K. Tully
- Infectious Disease Dynamics Unit, Melbourne School of Population and Global Health, The University of Melbourne, Melbourne, Australia
| | - Inke N. D. Lubis
- Department of Paediatrics, Faculty of Medicine, Universitas Sumatera Utara, Medan, Indonesia
| | - Rintis Noviyanti
- Eijkman Research Center for Molecular Biology, BRIN, Jakarta, Indonesia
| | - Nicholas M. Anstey
- Menzies School of Health Research and Charles Darwin University, Darwin, Australia
| | - Giri S. Rajahram
- Infectious Diseases Society Kota Kinabalu Sabah, Menzies School of Health Research, Clinical Research Unit, Hospital Queen Elizabeth II, and Clinical Research Centre, Queen Elizabeth Hospital, Ministry of Health, Kota Kinabalu, Malaysia
| | - Matthew J. Grigg
- Menzies School of Health Research and Charles Darwin University, Darwin, Australia
| | - Jennifer A. Flegg
- School of Mathematics and Statistics, The University of Melbourne, Melbourne, Australia
| | - David J. Price
- Infectious Disease Dynamics Unit, Melbourne School of Population and Global Health, The University of Melbourne, Melbourne, Australia
- Doherty Institute for Infection and Immunity, The Royal Melbourne Hospital and The University of Melbourne, Melbourne, Australia
| | - Freya M. Shearer
- Infectious Disease Dynamics Unit, Melbourne School of Population and Global Health, The University of Melbourne, Melbourne, Australia
- Infectious Disease Ecology and Modelling Group, Telethon Kids Institute, Perth, Australia
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Tobin RJ, Harrison LE, Tully MK, Lubis IND, Noviyanti R, Anstey NM, Rajahram GS, Grigg MJ, Flegg JA, Price DJ, Shearer FM. Updating estimates of Plasmodium knowlesi malaria risk in response to changing land use patterns across Southeast Asia. MEDRXIV : THE PREPRINT SERVER FOR HEALTH SCIENCES 2023:2023.08.04.23293633. [PMID: 37609228 PMCID: PMC10441477 DOI: 10.1101/2023.08.04.23293633] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 08/24/2023]
Abstract
Background Plasmodium knowlesi is a zoonotic parasite that causes malaria in humans. The pathogen has a natural host reservoir in certain macaque species and is transmitted to humans via mosquitoes of the Anopheles Leucosphyrus Group. The risk of human P. knowlesi infection varies across Southeast Asia and is dependent upon environmental factors. Understanding this geographic variation in risk is important both for enabling appropriate diagnosis and treatment of the disease and for improving the planning and evaluation of malaria elimination. However, the data available on P. knowlesi occurrence are biased towards regions with greater surveillance and sampling effort. Predicting the spatial variation in risk of P. knowlesi malaria requires methods that can both incorporate environmental risk factors and account for spatial bias in detection. Methods & Results We extend and apply an environmental niche modelling framework as implemented by a previous mapping study of P. knowlesi transmission risk which included data up to 2015. We reviewed the literature from October 2015 through to March 2020 and identified 264 new records of P. knowlesi, with a total of 524 occurrences included in the current study following consolidation with the 2015 study. The modelling framework used in the 2015 study was extended, with changes including the addition of new covariates to capture the effect of deforestation and urbanisation on P. knowlesi transmission. Discussion Our map of P. knowlesi relative transmission suitability estimates that the risk posed by the pathogen is highest in Malaysia and Indonesia, with localised areas of high risk also predicted in the Greater Mekong Subregion, The Philippines and Northeast India. These results highlight areas of priority for P. knowlesi surveillance and prospective sampling to address the challenge the disease poses to malaria elimination planning.
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Affiliation(s)
- Ruarai J Tobin
- Infectious Disease Dynamics Unit, Melbourne School of Population and Global Health, The University of Melbourne, Melbourne, Australia
| | - Lucinda E Harrison
- School of Mathematics and Statistics, The University of Melbourne, Melbourne, Australia
| | - Meg K Tully
- Infectious Disease Dynamics Unit, Melbourne School of Population and Global Health, The University of Melbourne, Melbourne, Australia
| | - Inke N D Lubis
- Department of Paediatrics, Faculty of Medicine, Universitas Sumatera Utara, Medan, Indonesia
| | - Rintis Noviyanti
- Eijkman Research Center for Molecular Biology, BRIN, Jakarta, Indonesia
| | - Nicholas M Anstey
- Menzies School of Health Research and Charles Darwin University, Darwin, Australia
| | - Giri S Rajahram
- Infectious Diseases Society Kota Kinabalu Sabah, Menzies School of Health Research Clinical Research Unit, Hospital Queen Elizabeth II, and Clinical Research Centre, Queen Elizabeth Hospital, Ministry of Health, Kota Kinabalu, Malaysia
| | - Matthew J Grigg
- Menzies School of Health Research and Charles Darwin University, Darwin, Australia
| | - Jennifer A Flegg
- School of Mathematics and Statistics, The University of Melbourne, Melbourne, Australia
| | - David J Price
- Infectious Disease Dynamics Unit, Melbourne School of Population and Global Health, The University of Melbourne, Melbourne, Australia
- Doherty Institute for Infection and Immunity, The Royal Melbourne Hospital and The University of Melbourne, Melbourne, Australia
| | - Freya M Shearer
- Infectious Disease Dynamics Unit, Melbourne School of Population and Global Health, The University of Melbourne, Melbourne, Australia
- Infectious Disease Ecology Modelling Group, Telethon Kids Institute, Perth, Australia
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Hope A, Mugenyi A, Esterhuizen J, Tirados I, Cunningham L, Garrod G, Lehane MJ, Longbottom J, Mangwiro TNC, Opiyo M, Stanton M, Torr SJ, Vale GA, Waiswa C, Selby R. Scaling up of tsetse control to eliminate Gambian sleeping sickness in northern Uganda. PLoS Negl Trop Dis 2022; 16:e0010222. [PMID: 35767572 PMCID: PMC9275725 DOI: 10.1371/journal.pntd.0010222] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2022] [Revised: 07/12/2022] [Accepted: 05/23/2022] [Indexed: 11/18/2022] Open
Abstract
Background Tsetse flies (Glossina) transmit Trypanosoma brucei gambiense which causes Gambian human African trypanosomiasis (gHAT) in Central and West Africa. Several countries use Tiny Targets, comprising insecticide-treated panels of material which attract and kill tsetse, as part of their national programmes to eliminate gHAT. We studied how the scale and arrangement of target deployment affected the efficacy of control. Methodology and principal findings Between 2012 and 2016, Tiny Targets were deployed biannually along the larger rivers of Arua, Maracha, Koboko and Yumbe districts in North West Uganda with the aim of reducing the abundance of tsetse to interrupt transmission. The extent of these deployments increased from ~250 km2 in 2012 to ~1600 km2 in 2015. The impact of Tiny Targets on tsetse populations was assessed by analysing catches of tsetse from a network of monitoring traps; sub-samples of captured tsetse were dissected to estimate their age and infection status. In addition, the condition of 780 targets (~195/district) was assessed for up to six months after deployment. In each district, mean daily catches of tsetse (G. fuscipes fuscipes) from monitoring traps declined significantly by >80% following the deployment of targets. The reduction was apparent for several kilometres on adjacent lengths of the same river but not in other rivers a kilometre or so away. Expansion of the operational area did not always produce higher levels of suppression or detectable change in the age structure or infection rates of the population, perhaps due to the failure to treat the smaller streams and/or invasion from adjacent untreated areas. The median effective life of a Tiny Target was 61 (41.8–80.2, 95% CI) days. Conclusions Scaling-up of tsetse control reduced the population of tsetse by >80% across the intervention area. Even better control might be achievable by tackling invasion of flies from infested areas within and outside the current intervention area. This might involve deploying more targets, especially along smaller rivers, and extending the effective life of Tiny Targets. Gambian human African trypanosomiasis (gHAT) is a neglected tropical disease caused by Trypanosoma brucei gambiense transmitted by tsetse flies (Glossina). Uganda’s strategy to eliminate gHAT includes the deployment of Tiny Targets, comprising insecticide-treated panels of cloth which attract and kill tsetse. Our data from a network of monitoring traps assessed how increasing the intervention area from ~250 km2 to ~1600 km2 affected the degree of control. Inspection of deployed targets indicated their effective lifespan. Targets reduced tsetse abundance by >80% beside the rivers where they were deployed but had no clear effect on adjacent rivers where targets were absent. As the intervention area increased, so did the extent of the area controlled. We did not deploy targets along the smaller rivers so that, as expected, the tsetse population was not eliminated. Our findings suggest that the population was sustained at low levels by invasion of tsetse from untreated parts of the drainage system. The average effective life of targets was ~60 days as against the ~180 days for targets deployed in Kenya. This discrepancy is attributable, in part, to the Uganda targets being removed by seasonal floods. While the level of control achieved is already more than sufficient to interrupt transmission of gHAT, even better control would be achieved by increasing the coverage of the drainage system.
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Affiliation(s)
- Andrew Hope
- Liverpool School of Tropical Medicine, Liverpool, Merseyside, United Kingdom
- * E-mail: (AH); (AM); (SJT)
| | - Albert Mugenyi
- Coordinating Office for Control of Trypanosomiasis in Uganda, Kampala, Uganda
- * E-mail: (AH); (AM); (SJT)
| | - Johan Esterhuizen
- Liverpool School of Tropical Medicine, Liverpool, Merseyside, United Kingdom
| | - Inaki Tirados
- Liverpool School of Tropical Medicine, Liverpool, Merseyside, United Kingdom
| | - Lucas Cunningham
- Liverpool School of Tropical Medicine, Liverpool, Merseyside, United Kingdom
| | - Gala Garrod
- Liverpool School of Tropical Medicine, Liverpool, Merseyside, United Kingdom
| | - Mike J. Lehane
- Liverpool School of Tropical Medicine, Liverpool, Merseyside, United Kingdom
| | - Joshua Longbottom
- Liverpool School of Tropical Medicine, Liverpool, Merseyside, United Kingdom
| | | | - Mercy Opiyo
- Liverpool School of Tropical Medicine, Liverpool, Merseyside, United Kingdom
- Barcelona Institute for Global Health, Hospital Clinic, Barcelona, Spain
| | - Michelle Stanton
- Liverpool School of Tropical Medicine, Liverpool, Merseyside, United Kingdom
| | - Steve J. Torr
- Liverpool School of Tropical Medicine, Liverpool, Merseyside, United Kingdom
- * E-mail: (AH); (AM); (SJT)
| | - Glyn A. Vale
- Southern African Centre for Epidemiological Modelling and Analysis, University of Stellenbosch, Stellenbosch, South Africa
- Natural Resources Institute, University of Greenwich, Chatham, United Kingdom
| | - Charles Waiswa
- Coordinating Office for Control of Trypanosomiasis in Uganda, Kampala, Uganda
| | - Richard Selby
- Liverpool School of Tropical Medicine, Liverpool, Merseyside, United Kingdom
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OUP accepted manuscript. Trans R Soc Trop Med Hyg 2022; 116:717-726. [DOI: 10.1093/trstmh/trac004] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2021] [Revised: 09/20/2021] [Accepted: 01/10/2022] [Indexed: 11/14/2022] Open
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Brown HE, Sedda L, Sumner C, Stefanakos E, Ruberto I, Roach M. Understanding Mosquito Surveillance Data for Analytic Efforts: A Case Study. JOURNAL OF MEDICAL ENTOMOLOGY 2021; 58:1619-1625. [PMID: 33615382 PMCID: PMC8285009 DOI: 10.1093/jme/tjab018] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/11/2020] [Indexed: 06/12/2023]
Abstract
Mosquito surveillance data can be used for predicting mosquito distribution and dynamics as they relate to human disease. Often these data are collected by independent agencies and aggregated to state and national level portals to characterize broad spatial and temporal dynamics. These larger repositories may also share the data for use in mosquito and/or disease prediction and forecasting models. Assumed, but not always confirmed, is consistency of data across agencies. Subtle differences in reporting may be important for development and the eventual interpretation of predictive models. Using mosquito vector surveillance data from Arizona as a case study, we found differences among agencies in how trapping practices were reported. Inconsistencies in reporting may interfere with quantitative comparisons if the user has only cursory familiarity with mosquito surveillance data. Some inconsistencies can be overcome if they are explicit in the metadata while others may yield biased estimates if they are not changed in how data are recorded. Sharing of metadata and collaboration between modelers and vector control agencies is necessary for improving the quality of the estimations. Efforts to improve sharing, displaying, and comparing vector data from multiple agencies are underway, but existing data must be used with caution.
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Affiliation(s)
- Heidi E Brown
- Department of Epidemiology and Biostatistics, Mel and Enid Zuckerman College of Public Health, University of Arizona, Tucson, AZ, USA
| | - Luigi Sedda
- Lancaster Medical School, Lancaster University, Bailrigg Campus, Lancaster, UK
| | - Chris Sumner
- Yuma County Pest Abatement District, Somerton, AZ, USA
| | | | - Irene Ruberto
- Arizona Department of Health Services, Office of Infectious Disease Services, Phoenix, AZ, USA
| | - Matthew Roach
- Arizona Department of Health Services, Office of Environmental Health, Phoenix, AZ, USA
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Longbottom J, Wamboga C, Bessell PR, Torr SJ, Stanton MC. Optimising passive surveillance of a neglected tropical disease in the era of elimination: A modelling study. PLoS Negl Trop Dis 2021; 15:e0008599. [PMID: 33651803 PMCID: PMC7954327 DOI: 10.1371/journal.pntd.0008599] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2020] [Revised: 03/12/2021] [Accepted: 02/07/2021] [Indexed: 11/19/2022] Open
Abstract
BACKGROUND Surveillance is an essential component of global programs to eliminate infectious diseases and avert epidemics of (re-)emerging diseases. As the numbers of cases decline, costs of treatment and control diminish but those for surveillance remain high even after the 'last' case. Reducing surveillance may risk missing persistent or (re-)emerging foci of disease. Here, we use a simulation-based approach to determine the minimal number of passive surveillance sites required to ensure maximum coverage of a population at-risk (PAR) of an infectious disease. METHODOLOGY AND PRINCIPAL FINDINGS For this study, we use Gambian human African trypanosomiasis (g-HAT) in north-western Uganda, a neglected tropical disease (NTD) which has been reduced to historically low levels (<1000 cases/year globally), as an example. To quantify travel time to diagnostic facilities, a proxy for surveillance coverage, we produced a high spatial-resolution resistance surface and performed cost-distance analyses. We simulated travel time for the PAR with different numbers (1-170) and locations (170,000 total placement combinations) of diagnostic facilities, quantifying the percentage of the PAR within 1h and 5h travel of the facilities, as per in-country targets. Our simulations indicate that a 70% reduction (51/170) in diagnostic centres still exceeded minimal targets of coverage even for remote populations, with >95% of a total PAR of ~3million individuals living ≤1h from a diagnostic centre, and we demonstrate an approach to best place these facilities, informing a minimal impact scale back. CONCLUSIONS Our results highlight that surveillance of g-HAT in north-western Uganda can be scaled back without substantially reducing coverage of the PAR. The methodology described can contribute to cost-effective and equable strategies for the surveillance of NTDs and other infectious diseases approaching elimination or (re-)emergence.
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Affiliation(s)
- Joshua Longbottom
- Department of Vector Biology, Liverpool School of Tropical Medicine, Liverpool, United Kingdom
- Centre for Health Informatics, Computing and Statistics, Lancaster Medical School, Lancaster University, Lancaster, United Kingdom
- * E-mail:
| | | | | | - Steve J. Torr
- Department of Vector Biology, Liverpool School of Tropical Medicine, Liverpool, United Kingdom
| | - Michelle C. Stanton
- Department of Vector Biology, Liverpool School of Tropical Medicine, Liverpool, United Kingdom
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